1. Field of the Invention
This invention relates to superconductive Josephson junction circuits. More particularly, the circuit relates to a novel Josephson junction voltage amplifier.
2. Cross Referenced to Related Applications
Our co-pending application Ser. No. 299,148 entitled "Three Josephson Junction Direct Coupled Isolation Circuit" is directed to an improvement fan-out current gain circuit capable of driving at least three identical output loads with a margin of safety to ensure proper operation.
3. Description of the Prior Art
The principal of operation of the above-mentioned circuit and other Josephson junction current gain circuits is based on current steering. It is well known that a Josephson junction device displays no impedance when the current passing through the junction is at a value less than the critical current I.sub.0. When a value of critical current I.sub.0 is reached, the Josephson junction becomes resistive and switches from the zero voltage state to the voltage gap state. The gap voltage for a Josephson junction remains constant and does not vary. When a constant current source is connected to a Josephson junction device, a major portion of that current can be steered or diverted to a parallel load or loads when the Josephson junction switches. The nature of a Josephson junction is that it either displays a voltage or no voltage; thus, by definition, it does not amplify an input voltage.
Josephson junction devices are classified as superconductive devices in U.S. Class 307, sub class 306. Josephson junction load drivers usually employ a plurality of parallel branches and a plurality of Josephson junction devices. All of these load drivers are limited to modest gain and modest fan-out. Circuits of this type are shown and described in IEEE Transactions on Magnetics, volume 15, no. 6, Nov. 1979 at pages 1876-1879 and also in IEEE International Electron Devices meeting, Washington, D.C., Dec. 3-5, 1979 at pages 482-484.
None of the aforementioned load driving Josephson junction circuits teach or suggest voltage amplification. Accordingly, it would be desirable to provide a new and improved Josephson junction circuit which operates as a high gain voltage amplifier.